Fluid-filled bladder for an article of footwear

ABSTRACT

The invention relates to a fluid-filled bladder and a method for making for making a fluid-filled bladder that include a core having at least one fusing filament. A portion of the fusing filament is positioned adjacent to the exterior surface of the core such that it engages and fuses to barrier layers of the bladder, thereby securing the core to the barrier layers without the need for an additional fusing agent therebetween.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a fluid-filled bladder suitable for footwearapplications. More particularly, the invention is a fluid-filled bladderhaving a core that includes strands of fusing agent to secure the coreto outer layers of the bladder.

2. Description of Background Art

Footwear is divided into two general parts, an upper and a sole. Theupper is designed to comfortably receive the foot and the sole providestraction, protection, and a durable wear-resistant surface. Theconsiderable forces generated during athletic activities require thatthe sole of footwear attenuate ground reaction forces and absorb energy,thereby providing protection to the foot and leg. Accordingly, the soleof athletic footwear typically has a layered structure that includes acomfort-enhancing insole, a resilient midsole, and a ground-contactingoutsole that provides both durability and traction.

Midsoles are traditionally formed of conventional foam materials such asethylene vinyl acetate or polyurethane that compress resiliently underan applied load to attenuate ground reaction forces and absorb energy.Conventional foam materials are resiliently compressible, in part, dueto the inclusion of a plurality of open or closed cells that define aninner volume substantially displaced by gas. That is, the foam includesbubbles formed in the material that enclose gas. After repeatedcompressions, however, the cell structure deteriorates, therebyresulting in decreased compressibility of the foam. Thus, the forceattenuation and energy absorption characteristics of the midsole maydecrease over the lifespan of the footwear.

One way to overcome the drawbacks of utilizing conventional foammaterials is disclosed in U.S. Pat. No. 4,183,156 to Rudy, herebyincorporated by reference, in which cushioning is provided by inflatableinserts formed of elastomeric materials. The inserts include a pluralityof tubular chambers that extend substantially longitudinally throughoutthe length of the footwear. The chambers are in fluid communication witheach other and jointly extend across the width of the footwear. U.S.Pat. No. 4,219,945 to Rudy, hereby incorporated by reference, disclosesan inflated insert encapsulated in a foam material. The combination ofthe insert and the encapsulating material functions as a midsole. Anupper is attached to the upper surface of the encapsulating material andan outsole or tread member is affixed to the lower surface.

Such bladders are generally formed of an elastomeric material and arestructured to have an upper or lower surface that encloses one or morechambers therebetween. The chambers are pressurized above ambientpressure by inserting a nozzle or needle connected to a fluid pressuresource into a fill inlet formed in the bladder. After the chambers arepressurized, the fill inlet is sealed, for example, by welding, and thenozzle is removed.

Bladders of this type have been manufactured by the prior art two-filmtechnique in which two separate sheets of elastomeric film are formedhaving the overall peripheral shape of the bladder. The sheets arewelded together along the periphery to form a bladder having upper,lower, and side surfaces, and the sheets are welded together atpredetermined interior areas to give the bladder a desiredconfiguration. That is, the interior welds provide the bladder withchambers having a predetermined shape and size at desired locations.

Bladders have also been manufactured by the prior art blow-moldingtechnique, wherein a liquefied elastomeric material is placed in a moldhaving the desired overall shape and configuration of the bladder. Themold has an opening at one location through which pressurized air isprovided. The pressurized air forces the liquefied elastomeric materialagainst the inner surfaces of the mold and causes the material to hardenin the mold, thereby forming a bladder with the desired shape andconfiguration.

Another type of prior art bladder used in soles of footwear is disclosedin U.S. Pat. Nos. 4,906,502 and 5,083,361, both to Rudy, and both herebyincorporated by reference. This type of bladder is formed as a fluidpressurized and inflated structure that comprises a hermetically sealedouter barrier layer which is securely fused substantially over theentire outer surfaces of a double-walled fabric core. The double-walledfabric core is comprised of first and second outer fabric layers thatare normally spaced apart from one another at a predetermined distance.Connecting or drop yarns, potentially in the form of multi-filamentyarns having many individual fibers, extend internally between theproximal or facing surfaces of the respective fabric layers. Thefilaments of the drop yarns form tensile restraining means and areanchored to the respective fabric layers. A suitable method ofmanufacturing the double walled fabric structure is double needle barRaschel knitting.

U.S. Pat. Nos. 5,993,585 and 6,119,371, both issued to Goodwin et al.,and both hereby incorporated by reference, disclose a bladder utilizinga double-walled fabric core, as with the '502 and '361 patents, butwithout a peripheral seam located midway between the upper and lowersurfaces of the bladder. Instead, the seam is located adjacent to theupper surface of the bladder. Advantages in this design include removalof the seam from the area of maximum sidewall flexing and increasedvisibility of the interior of the bladder, including the connectingyarns. The process utilized to form a bladder of this type involves theformation of a shell, which includes a lower surface and a sidewall,with a mold. A double-walled fabric core is placed on top of a coveringsheet, and the shell, following removal from the mold, is placed overthe covering sheet and core. The assembled shell, covering sheet, andcore are then moved to a lamination station where radio frequency energyfuses opposite sides of the core to the shell and covering sheet andfuses a periphery of the shell to the covering sheet. The bladder isthen pressurized by inserting a fluid so as to place the connectingyarns in tension.

Another type of prior art bladder used in soles of footwear is disclosedin U.S. Pat. No. 4,874,640 to Donzis, and U.S. Pat. Nos. 5,741,568 and6,127,010 to Rudy, all of which are hereby incorporated by reference.This type of bladder utilizes a compressible insert encapsulated withinan elastomeric barrier member. In the '640 patent, the elastomericbarrier member is generally impermeable to air and generally filled witha fluid that can be pressurized. The insert includes a compression,impact absorbing foam core glued or fused on its external surfaces tothe elastomeric barrier member. The internal foam cushioning member canbe reinforced by including filaments, fibers, or fabrics within the foamcore. The '568 and '101 patents suggest various materials can be usedfor the compressible insert, including cotton, rubber, foam, horsehair,plastic mesh, etc. A preferred material is identified as at leastpartially open cell, flexible foam, such as polyurethane orethylene-vinyl acetate. Filaments are utilized to enhance the connectionbetween the compressible insert and the barrier member, with portions ofthe filaments being imbedded in both the compressible insert and thebarrier material. Examples of suitable filaments are listed aspolyesters, polyethylene terephthalate, polyamides, nylons, fiberglass,carbon, glass, silk, cotton, wool, urethane, aramid, Dacron, cellulose,rayon, copra, acetate, polyvinyl alcohol, polyacrylics, and mixturesthereof.

While the cushioning benefits of bladders in articles of footwear arewell documented, the prior art methods of manufacturing bladdersutilizing a double-walled fabric core have made them costly and timeconsuming to manufacture. In particular, the double-walled fabric coreis typically secured within the bladder by attaching a layer ofthermally activated fusing agent to the outer surfaces of the core, andthen heating the bladder components to cause the fusing agent to melt,thereby securing the core the outer layers of the bladder. In practice,it is time consuming to add the fusing agent to the outer surfaces ofthe core and requires additional manufacturing steps, thereby increasingoverall cost. Accordingly, the art requires a simple, cost effectivemethod for securing a double-walled fabric core within a bladder. Inaddition to other benefits that will become apparent from the followingdisclosure, the present invention fulfills this need.

SUMMARY OF THE INVENTION

The present invention relates to a fluid-filled bladder, and a methodfor forming a fluid-filled bladder, that is suitable for use with anarticle of footwear. The bladder includes an outer barrier and a core.The outer barrier is substantially impermeable to a fluid contained bythe bladder. The core is located within the outer barrier and includesat least one fusing filament that fuses with the outer barrier andsecures the core to the outer barrier.

Conventional cores were formed through a double needle bar Raschelknitting process. A sheet of fusing agent was then applied to the outerlayers of the cores. The fusing filament of the present invention,however, may be integrated into the structure of the walls, throughweaving for example, thereby eliminating the manufacturing step ofapplying the fusing agent to the outer layers.

The fusing filament and the barrier layers may be a thermoplasticmaterial that is heated to a temperature that softens the material, butis below the melting point. Subsequent contact and cooling of thematerials will effectively fuse the materials and secure the core to thebarrier layers.

The advantages and features of novelty characterizing the presentinvention are pointed out with particularity in the appended claims. Togain an improved understanding of the advantages and features ofnovelty, however, reference may be made to the following descriptivematter and accompanying drawings that describe and illustrate variousembodiments and concepts related to the invention.

DESCRIPTION OF THE DRAWINGS

The foregoing Summary of the Invention, as well as the followingDetailed Description of the Invention, will be better understood whenread in conjunction with the accompanying drawings.

FIG. 1 is a lateral elevational view of an article of footwear having abladder in accordance with the present invention.

FIG. 2 is a top plan view of a bladder in accordance with the presentinvention.

FIG. 3 is a cross-sectional view of the bladder as defined by line 3-3in FIG. 2.

FIG. 4 is a perspective diagrammatic view of a material that forms acore in accordance with the present invention.

FIG. 5 is a cross-sectional view of the bladder, as depicted in FIG. 3,but prior to attachment of the core to the outer layers of the bladder.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the figures and following discussion, wherein like numeralsindicate like elements, an article of footwear and a bladder inaccordance with the present invention are disclosed. FIG. 1 depicts anarticle of footwear 100 having an upper 110 and a sole 120. A bladder200 is located in a heel portion of sole 120 to provide enhanced groundreaction force attenuation and energy absorption. Article of footwear100 is depicted as an athletic shoe. Bladder 200 may, however, beutilized in other types of footwear, including dress shoes, sandals,boots, and in-line skates.

Bladder 200, depicted individually in FIGS. 2 and 3, includes an outerbarrier, is formed of a first barrier layer 210 a, a second barrierlayer 210 b, and a core 220 that is positioned between barrier layers210 a and 210 b. First barrier layer 210 a is attached to second barrierlayer 210 b around their respective peripheries to form a peripheralbond 212. Accordingly, barrier layers 210 a and 210 b and peripheralbond 212 form a sealed, fluid-filled chamber that encloses core 220.

Barrier layers 210 a and 210 b are formed of a thermoplastic elastomermaterial that is substantially impermeable to the fluid contained bybladder 200. The material forming barrier layers 210 a and 210 b may be,for example, a film formed of alternating layers of thermoplasticpolyurethane and ethylene-vinyl alcohol copolymer, as disclosed in U.S.Pat. Nos. 5,713,141 and 5,952,065 to Mitchell et al, incorporated byreference. A variation upon this material wherein the center layer isformed of ethylene-vinyl alcohol copolymer; the two layers adjacent tothe center layer are formed of thermoplastic polyurethane; and the outerlayers are formed of a regrind material of thermoplastic polyurethaneand ethylene-vinyl alcohol copolymer may also be utilized for barrierlayers 210 a and 210 b. Another suitable material is a flexiblemicrolayer membrane that includes alternating layers of a gas barriermaterial and an elastomeric material, as disclosed in U.S. Pat. Nos.6,082,025 and 6,127,026 to Bonk et al., hereby incorporated byreference. Other suitable thermoplastic elastomer materials or filmsinclude polyurethane, polyester, polyester polyurethane, polyetherpolyurethane, such as cast or extruded ester-based polyurethane filmhaving a shore A hardness of 85-90, e.g., Tetra Plastics TPW-250.Additional suitable materials are disclosed in U.S. Pat. Nos. 4,183,156and 4,219,945 to Rudy. Among the numerous thermoplastic urethanes thatare useful in forming the film sheets are urethanes such as PELLETHANE,a product of the Dow Chemical Company; ELASTOLLAN, a product of the BASFCorporation; and ESTANE, a product of the B.F. Goodrich Company, all ofwhich are either ester or ether based. Still other thermoplasticurethanes based on polyesters, polyethers, polycaprolactone, andpolycarbonate macrogels may be employed. Nitrogen blocking barriermaterials may also be utilized and include PVDC, also known as SURAN;nylon; EVOH; and PVDF, also known as KYNAR. Further suitable materialsinclude thermoplastic films containing a crystalline material, asdisclosed in U.S. Pat. Nos. 4,936,029 and 5,042,176 to Rudy, herebyincorporated by reference, and polyurethane including a polyesterpolyol, as disclosed in U.S. Pat. Nos. 6,013,340; 6,203,868; and6,321,465 to Bonk et al., hereby incorporated by reference.

Core 220 includes a first wall 222 a that is normally spaced apart froma second wall 222 b at a predetermined distance. A plurality ofconnecting members 224 extend between first wall 222 a and second wall222 b. When a fluid pressurizes bladder 200, the fluid places an outwardforce on barrier layers 210 a and 210 b. The outward force extendsconnecting members 224, thereby placing connecting members 224 intension and restraining further outward movement of barrier layers 210 aand 210 b. A material from which core 220 may be cut is depicted in FIG.4. Connecting members 224 may be comprised of drop yams that eachinclude multiple tensile filaments that are anchored to first wall 222 aand second wall 222 b. One method of manufacturing core 220 is doubleneedle bar Raschel knitting. A portion of first wall 222 a and secondwall 222 b may be formed of air-bulked or otherwise texturized yarn,such as false twist texturized yarn having a combination of Nylon 6,6and Nylon 6. Connecting members 224 may be formed of a similar material.As will be discussed in detail below, first wall 222 a and second wall222 b also include fusing filaments. Although the thickness of core 220,which is measured when connecting members 224 are in a tensile statebetween first wall 222 a and second wall 222 b, may vary significantlywithin the scope of the present invention, a thickness that is suitablefor footwear applications may range from 8 to 15 millimeters.

Connecting members 224 may have a denier per filament of approximately 1to 20 with one suitable range being between 2 and 5. The individualtensile filaments that comprise connecting members 224 may exhibit atensile strength of approximately 2 to 10 grams per denier and thenumber of tensile filaments per yarn ranges from approximately 1 to 100with one suitable range being between 40 and 60. In general, there areapproximately 1 to 8 yarns per tuft or strand and core 200 is knittedwith approximately 200 to 1000 tufts or strands per square inch offabric, with one suitable range being between 400 to 500 strands persquare inch. The bulk density of the fabric is, therefore, in the rangeof about 20,000 to 300,000 fibers per square inch—denier.

Connecting members 224 may be arranged in rows that are separated bygaps. The use of gaps provides core 220 with increased compressibilityin comparison to cores formed of double-walled fabrics that utilizecontinuous connecting yams. The gaps may be formed during the doubleneedle bar Raschel knitting process by omitting connecting yams oncertain predetermined needles in the warp direction. Knitting with threeneedles in and three needles out produces a suitable fabric with rows ofconnecting members 224 being separated by gaps. Other knitting patternsof needles in and needles out can be used, such as two in and two out,four in and two out, two in and four out, or any combination thereof.Also, the gaps may be formed in both a longitudinal and transversedirection by omitting needles in the warp direction or selectivelyknitting or not knitting on consecutive courses. Core 220, as depictedin FIG. 4, has relatively large gaps between connecting members 224.Alternatively, the gaps may be smaller or connecting members 224 mayextend throughout core 220. The above-mentioned '585 and '371 Goodwin,et al patents disclose fabric bladder cores with gaps between rows ofconnecting members, while the '502 and '361 Rudy patents disclose fabricbladder cores with connecting members located throughout the core.

As discussed in the Description of Background Art section above,double-walled fabric cores are typically secured within an outer barrierof a bladder by attaching a layer of thermally activated fusing agent tothe first wall and second wall of the core, and then heating the outerbarrier, core, and fusing agent to cause the fusing agent to fuse thewalls of the core to the outer barrier. The thermally activated fusingagent is typically a sheet of thermoplastic material that is heated andpressed into contact with the first wall and the second wall prior toplacing the core between layers of the outer barrier. Although thisprocess could be utilized to effectively secure core 220 and barrierlayers 210 a and 210 b to each other, this process adds a manufacturingstep and additional expense to the manufacturing process.

In contrast with the method discussed above, the present inventionutilizes a plurality of fusing filaments 230 that are integrated intofirst wall 222 a and second wall 222 b, through weaving for example.Fusing filaments 230 are formed of a material that will fuse, bond, orotherwise become secured to barrier layers 210 a and 210 b when thevarious components of bladder 200 are heated and compressed together.Suitable materials for fusing filaments 230 include, therefore,thermoplastic polyurethane or any of the materials that are suitable forbarrier layers 210 a and 210 b, as discussed above. Fusing filaments 230may be woven or otherwise mechanically manipulated into walls 222 a and222 b during the double needle bar Raschel knitting process or followingthe knitting process. Accordingly, fusing filaments 230 may beintegrated into walls 222 a and 222 b during the manufacturing processof core 220, or fusing filaments 230 may be subsequently added to walls222 a and 222 b.

The configuration of fusing filaments 230 and the manner in which fusingfilaments 230 are integrated into walls 222 a and 222 b may vary greatlywithin the scope of the present invention. Fusing filaments 230 may befibers, filaments, yams, strips, or elements of material that areelongate and are integrated into first and second walls 222 a and 222 b.The term “fusing filaments” is, therefore, intended to encompass a broadrange of types of material and material geometries that permit thematerial to be integrated into walls 222 a and 222 b. In contrast withthe fusing agent utilized in prior art bladders, however, fusingfilaments 230 are not sheets of material that are heat fused to theexterior surfaces of the core. FIGS. 2 and 4 depict fusing filaments asextending in a first, longitudinal direction and in a second directionthat is transverse to the first direction. Fusing filaments 230 may alsoextend in only one direction, extend in a plurality of directions, orextend in random directions, for example. Fusing filaments can beincorporated into the first and second walls by any conventionalmechanical manipulation technique such as interweaving, intertwining,and twisting or interlooping, with knitting being the most common methodof interlooping. For example, as mentioned above, when core 220 is madeby double needle bar Raschel knitting, filaments 230 are knit into thewalls 220 a and 220 b. Thermoplastic polyurethane fibers are onesuitable type of fusing filament. Examples of such fibers are OptimerEcothane and BFG/Hualon manufactured by Optimer Performance Materials,Inc. of Wilmington, Del.

A method of attaching core 220 to barrier layers 210 a and 210 b, andthereby forming bladder 200, will now be discussed. As depicted in FIG.5, core 220 is positioned between barrier layers 210 a and 210 b suchthat portions of fusing filaments 230 located along the outer surfacesof walls 220 are located adjacent to the inner surfaces of barrierlayers 210 a and 210 b. At least barrier layers 210 a and 210 b andfusing filaments 230 are then heated and brought into contact such thatfusing occurs between fusing filaments 230 and barrier layers 210 a and210 b. Heating may be achieved through a variety of processes, includingirradiating the components with radio frequency energy, compressing thecomponents between platens of a hot press, positioning the components ina conventional radiant heater oven, ultrasonic welding, and UV directheating, for example. Following heating, the components are cooled. Inthis manner, core 220 becomes effectively fused to barrier layers 210 aand 210 b.

The temperature to which barrier layers 210 a and 210 b and filaments230 are heated depends upon the specific materials utilized for fusingfilaments 230 and barrier layers 210 a and 210 b. In general, thematerials of the barrier layers 210 a and 210 b and fusing filaments 230should be heated to a degree that exceeds the softening temperature, butis below the melting point, thereby ensuring proper fusing. As notedabove, barrier layers 210 a and 210 b and filaments 230 may be formedfrom a variety of materials. In addition, barrier layers 210 a and 210 band filaments 230 may be formed from different materials. One suitablematerial for barrier layers 210 a and 210 b is alternating layers ofthermoplastic polyurethane and ethylene-vinyl alcohol copolymer, whichhas a melting temperature between 350 and 360 degrees Fahrenheit. Thetemperature to which the first material should be heated is, therefore,between 300 and 320 degrees Fahrenheit. Another suitable material forbarrier layers 210 a and 210 b is a flexible microlayer membrane thatincludes alternating layers of a gas barrier material and an elastomericmaterial, such as thermoplastic polyurethane, which also has a meltingtemperature in the range of 350 to 360 degrees Fahrenheit. A suitabletemperature to which the second material may be heated is, however,between 320 and 335 degrees Fahrenheit. One skilled in the relevant artwill recognize, therefore, that the proper heating temperature dependsupon the materials that comprise barrier layers 210 a and 210 b andfilaments 230.

Peripheral bond 212 is also formed by compressing and heat sealingbarrier layers 210 a and 210 b together around substantially the entireperiphery of core 220. Alternatively, barrier layer 210 b may bepreshaped to the configuration depicted in FIG. 3, and barrier layer 210a, which is in sheet form, may be attached to the peripheral edges andsealed, as disclosed in U.S. Pat. No. 5,993,585 to Goodwin et al. Afluid, preferably air, is then injected into the area encompassed bybarrier layers 210 a and 210 b at a relatively high pressure, forexample between 60 and 80 pounds per square inch, in order topre-inflate and expand the core. The pressurized air is expired from thebladder and the intended permanent inflation gas is inserted at thedesired pressure, for example from 5 to 30 pounds per square inch.Finally, the injection port is sealed, thereby pressurizing bladder 200.As depicted in FIGS. 2 and 3, peripheral bond 212 is substantiallylocated on the plane of first barrier layer 210 a. This configurationremoves the seam from the are of maximum sidewall flexing and provides amore aesthetic structure in that the sidewall of bladder 200 is notobscured by a seam. Peripheral bond 212 may, however, be located on aplane that is located between barrier layers 210 a and 210 b. To assurethat connecting member 224 adequately connects first and second walls222 a and 222 b, and that walls 222 a and 222 b are adequately fused tobarrier layers 210 a and 210 b, a peel test under ASTM T-Peel Test D1876is performed. Peel strengths between 25 and 40 pounds per square inchare sufficient. As an alternative to the general method discussed above,a thermoforming technique may be utilized, as disclosed in U.S. patentapplication Ser. No. 09/995,003, entitled Method of Thermoforming aBladder Structure and filed Nov. 26, 2001.

Bladder 200 gains a variety of advantages over prior art bladders. Forexample, the overall weight and stiffness (resistance to bending) ofbladder 200 are reduced; material costs will decrease because a lesserquantity of fusing material is required; a more consistent bladder maybe produced as a manufacturing step is eliminated; and processefficiency will increase due to the removal of the manufacturing step.

The present invention is disclosed above and in the accompanyingdrawings with reference to a variety of embodiments. The purpose servedby the disclosure, however, is to provide an example of the variousfeatures and concepts related to the invention, not to limit the scopeof the invention. One skilled in the relevant art will recognize thatnumerous variations and modifications may be made to the embodimentsdescribed above without departing from the scope of the presentinvention, as defined by the appended claims.

1. A fluid-filled bladder for an article of footwear, the bladder comprising: a flexible outer barrier that is substantially impermeable to a fluid contained by the bladder; and a core located within the outer barrier, the core including at least one fusing filament that fuses with the outer barrier and secures the core to the outer barrier.
 2. The fluid-filled bladder of claim 1, wherein the core includes a first wall structure that is spaced from a second wall structure, the wall structures being joined by a plurality of connecting members.
 3. The fluid-filled bladder of claim 2, wherein the core is manufactured through a double needle bar Raschel knitting process.
 4. The fluid-filled bladder of claim 2, wherein the at least one fusing filament is integrated into the wall structures.
 5. The fluid-filled bladder of claim 2, wherein the at least one fusing filament is mechanically manipulated into the first and second wall structures.
 6. The fluid-filled bladder of claim 1, wherein the at least one fusing filament and the outer barrier are formed of thermoplastic materials fused to one another.
 7. The fluid-filled bladder of claim 1, wherein the at least one fusing filament is formed from thermoplastic polyurethane.
 8. The fluid-filled bladder of claim 1, wherein the outer barrier is formed of a first barrier layer and a second barrier layer that are fused together around a periphery of the core.
 9. A fluid-filled bladder for an article of footwear, the bladder comprising: a flexible outer barrier that is substantially impermeable to a fluid contained by the bladder; and a core located within the outer barrier, the core including a first wall structure that is spaced from a second wall structure, the wall structures being joined by a plurality of connecting members, and the core including at least one fusing filament that is integrated into the wall structures and fuses with the outer barrier to secure the core to the outer barrier.
 10. The fluid-filled bladder of claim 9, wherein the at least one fusing filament is mechanically manipulated into the wall structures.
 11. The fluid-filled bladder of claim 9, wherein the core is manufactured through a double needle bar Raschel knitting process.
 12. The fluid-filled bladder of claim 9, wherein the at least one fusing filament and the outer barrier are formed of a thermoplastic materials.
 13. The fluid-filled bladder of claim 9, wherein the at least one fusing filament and the outer barrier are formed to the same type of thermoplastic material.
 14. The fluid-filled bladder of claim 9, wherein the at least one fusing filament is formed from thermoplastic polyurethane.
 15. The fluid-filled bladder of claim 9, wherein the outer barrier is formed of a first barrier layer and a second barrier layer that are fused together around a periphery of the core.
 16. A method for forming a fluid-filled bladder for an article of footwear, the method comprising steps of: positioning a core between a first barrier layer and a second barrier layer; heating the core and the barrier layers such that a fusing filament integrated into the core fuses with the barrier layers; and forming a peripheral bond between the barrier layers, the peripheral bond being located substantially around a periphery of the core.
 17. The method for forming a fluid-filled bladder of claim 16, further including a step of manufacturing the core to include a first wall structure that is spaced from a second wall structure, the first and second wall structures being joined by a plurality of connecting members.
 18. The method for forming a fluid-filled bladder of claim 17, wherein the step of manufacturing the core includes mechanically manipulating the fusing filament into the wall structures.
 19. The method for forming a fluid-filled bladder of claim 17, wherein the step of manufacturing the core includes positioning at least a portion of the fusing filament opposite the connecting members.
 20. The method for forming a fluid-filled bladder of claim 17, wherein the step of manufacturing the core includes selecting a material of the fusing filament to be identical to a material selected for the barrier layers.
 21. The method for forming a fluid-filled bladder of claim 17, wherein the step of manufacturing the core includes selecting a material of the fusing filament to be thermoplastic polyurethane.
 22. The method for forming a fluid-filled bladder of claim 16, wherein the step of heating includes utilizing one of the group selected from radio frequency energy, platens of a hot press, ultrasonic welding, UV direct heating, and a radiant heater oven to elevate a temperature of the core and the barrier layers.
 23. The method for forming a fluid-filled bladder of claim 16, further including a step of pressurizing the bladder by injecting a fluid into an area between the barrier layers.
 24. A method for forming a fluid-filled bladder for an article of footwear, the method comprising steps of: manufacturing a core that includes a first wall structure spaced from a second wall structure, the first and second wall structures being joined by a plurality of connecting members, and the core including a fusing filament integrated into the wall structures; positioning the core between a first barrier layer and a second barrier layer; heating the core and the barrier layers such that the fusing filament in the core fuses with the barrier layers; forming a peripheral bond between the barrier layers to form a chamber around the core, the peripheral bond being located substantially around a periphery of the core; injecting a gas into the chamber to place the connecting members in tension, the gas having a pressure above atmospheric pressure; and sealing the chamber.
 25. The method for forming a fluid-filled bladder of claim 24, wherein the step of manufacturing the core includes mechanically manipulating the fusing filament into the wall structures.
 26. The method for forming a fluid-filled bladder of claim 25, wherein the step of manufacturing the core includes forming the core through double needle bar Raschel knitting.
 27. The method for forming a fluid-filled bladder of claim 24, wherein the step of manufacturing the core includes positioning at least a portion of the fusing filament on the walls opposite the connecting members.
 28. The method for forming a fluid-filled bladder of claim 24, wherein the step of manufacturing the core includes selecting a material of the fusing filament to be identical to a material selected for the barrier layers.
 29. The method for forming a fluid-filled bladder of claim 24, wherein the step of manufacturing the core includes selecting a material of the fusing filament to be thermoplastic polyurethane.
 30. An article of footwear comprising: an upper for receiving a foot of a wearer; and a sole structure attached to the upper, the sole structure including a midsole and an outsole that is attached to the midsole, the midsole incorporating a fluid-filled and pressurized bladder that includes: an outer barrier and a core, the outer barrier being formed of a first barrier layer and a second barrier layer that are fused together around a periphery of the core, the outer barrier being substantially impermeable to a fluid contained by the bladder, and the core being located within the outer barrier, the core including a first wall structure that is spaced from a second wall structure, the wall structures being joined by a plurality of connecting members, and the core including at least one fusing filament that is integrated into the wall structures and fuses with the outer barrier to secure the core to the outer barrier.
 31. The article of footwear of claim 30, wherein the at least one fusing filament is mechanically manipulated into the wall structures.
 32. The article of footwear of claim 31, wherein the core is manufactured through a double needle bar Raschel knitting process.
 33. The article of footwear of claim 30, wherein the at least one fusing filament and the outer barrier are formed of thermoplastic materials.
 34. The article of footwear of claim 33, wherein the at least one fusing filament is formed from thermoplastic polyurethane.
 35. The article of footwear of claim 34, wherein the first and second barrier layers are formed from thermoplastic polyurethane.
 36. A method for manufacturing an article of footwear, the method comprising steps of: positioning a core between a first barrier layer and a second barrier layer; heating the core and the barrier layers such that a fusing filament integrated into the core fuses with the barrier layers; forming a peripheral bond between the barrier layers, the peripheral bond being located substantially around a periphery of the core; integrating the core and barrier layers into a sole structure; and attaching the sole structure to an upper.
 37. The method for manufacturing an article of footwear of claim 36, further including a step of manufacturing the core to include a first wall structure that is spaced from a second wall structure, the first and second wall structures being joined by a plurality of connecting members.
 38. The method for manufacturing an article of footwear of claim 37, wherein the step of manufacturing the core includes mechanically manipulated the fusing filament into the wall structures.
 39. The method for manufacturing an article of footwear of claim 38, wherein the first wall structure, the second wall structure, the connecting member, and the fusing filaments are knit to one another by double needle bar Raschel knitting.
 40. The method for manufacturing an article of footwear of claim 39, wherein the step of manufacturing the core includes selecting a material of the fusing filament to be identical to a material selected for the barrier layers.
 41. The method for manufacturing an article of footwear of claim 37, wherein the step of manufacturing the core includes selecting a material of the fusing filament to be thermoplastic polyurethane.
 42. The method for manufacturing an article of footwear of claim 37, further including a step of pressurizing the bladder by injecting a fluid into an area between the barrier layers.
 43. A pressurized bladder for an article of footwear, the bladder comprising: an outer barrier formed of a first sheet and a second sheet of thermoplastic material, the first sheet and the second sheet being joined at their respective peripheries to form a sealed chamber, the first sheet and the second sheet being substantially impermeable to a pressurized gas contained by the chamber at a pressure of at least 5 pounds per square inch; and a core located within the chamber, the core including a first fabric layer attached to the first sheet and a second fabric layer attached to the second sheet, the first fabric layer and the second fabric layer being spaced apart and connected together by a plurality of connecting yarns that extend between the first fabric layer and the second fabric layer, and the first fabric layer and the second fabric layer each including fusing filaments formed of a thermoplastic material, the fusing filaments being mechanically manipulated into the first fabric layer and the second fabric layer over a sufficient surface area to form a fused attachment that secures the first fabric layer to the first sheet and secures the second fabric layer to the second sheet when the chamber is pressurized to at least 5 pounds per square inch with a peel strength of at least 5 pounds per linear inch between the fabric layers and the outer barrier.
 44. The pressurized bladder of claim 43, wherein the core is manufactured through a double needle bar Raschel knitting process.
 45. The pressurized bladder of claim 43, wherein the fusing filaments are formed from thermoplastic polyurethane.
 46. A method for forming a fluid-filled bladder for an article of footwear, the method comprising steps of: manufacturing a core by forming a first fabric layer spaced from a second fabric layer with thermoplastic fusing filaments mechanically manipulated into each of the fabric layers, and the fabric layers being joined by a plurality of connecting yams; positioning the core between a first sheet of thermoplastic material and a second sheet of thermoplastic material; heating the core and the sheets of thermoplastic material such that the thermoplastic fusing filaments in the first fabric layer fuse with the first sheet of thermoplastic material, and the thermoplastic fusing filaments in the second fabric layer fuse with the second sheet of thermoplastic material with a peel strength between the fabric layers and the sheets of at least 5 pounds per linear inch; forming a peripheral bond between the sheets of thermoplastic material, the peripheral bond being located around a periphery of the core; and injecting a fluid into the bladder to pressurize the bladder to at least 5 pounds per square inch and to place the connecting yams in tension.
 47. The method for forming a fluid-filled bladder of claim 46, wherein the step of manufacturing the core includes selecting a material of the thermoplastic fusing filaments to be identical to a material selected for the sheets of thermoplastic material.
 48. The method for forming a fluid-filled bladder of claim 46, wherein the step of manufacturing the core includes selecting a material of the thermoplastic fusing filaments to be thermoplastic polyurethane.
 49. The method for forming a fluid-filled bladder of claim 43, wherein the step of heating includes utilizing one of the group selected from radio frequency energy, platens of a hot press, ultrasonic welding, UV direct heating, and a radiant heater oven to elevate a temperature of the core and the sheets of thermoplastic material.
 50. The method for forming a fluid-filled bladder of claim 46, wherein the step of manufacturing the core includes knitting the first fabric layer, the second fabric layer, the thermoplastic fusing filaments, and the connecting yams by double needle bar Raschel knitting. 